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Forum: Geometry
Re: Question Potential overlapping causing unexpected results (Vince P.)
Re: More Re: Potential overlapping causing unexpected results (Gabriele Cosmo)
Date: 25 Jun, 2015
From: Vince P. <Vince P.>

Hi Gabriele,

I appreciate the reply. Thankfully this issue was resolved about a month
ago. If you are interested in the details, see:

https://groups.cern.ch/group/atlas-simulation/Lists/Archive/Flat.aspx?RootFolder=%2Fgroup%2Fatlas-simulation%2FLists%2FArchive%2FGeometry%20and%20calculator%20implementation%20yielding%20expected%20results%20from%20simulation&FolderCTID=0x01200200ECB55EE754BB494DAEF0F9693C514D0B

and

https://groups.cern.ch/group/atlas-simulation/Lists/Archive/Flat.aspx?RootFolder=%2Fgroup%2Fatlas-simulation%2FLists%2FArchive%2FGeometry%20and%20calculator%20implementation%20yielding%20expected%20results%20from%20simulation%208385&FolderCTID=0x01200200ECB55EE754BB494DAEF0F9693C514D0B

The last post on the latter link contains a brief overview of the
original problem as well as the solution.


Best,
Vince.

On Thu, 2015-06-25 at 07:40 -0700, Gabriele Cosmo wrote:
> *** Discussion title: Geometry
> 
> Hi Vince,
> 
> overlaps should always be avoided, especially when these apply to
> sensitive volumes, as it appears to be in your case. So, please
> verify your geometry is free from overlaps using the provided tools!
> The other thing which can be problematic when using Boolean subtractions,
> is the presence of shared surfaces between the components being subtracted
> which may lead to numerical instabilities, therefore better to avoid them by
> properly composing the Boolean operation, if at all possible.
> Hope it helps!
> 
> Cheers, Gabriele
> 
> --------------
> On Thu, 14 May 2015 17:46:23 GMT, Vince P. wrote:
> > Hi,
> > 
> > I am implementing a liquid argon calorimeter using GEANT4. Included are
> > attachments of screenshots of my geometry. The calorimeter is the small
> > portion to the left of the purple cylinder in attachments g4-ss1 and
> > g4-ss3.
> > 
> > Basically I have a mother volume in which I add two daughters, a solid
> > cylinder of radius 40mm (c1, purple) and another hollow cylinder
> > constructed using Pcons (c2, grey) with two radii, rmin=50mm and
> > rmax=370mm. c1 passes through c2 as shown in attachments g4-ss1 and
> > g4ss3. Now, c2 has the portion of the volume removed where c1 is
> > inserted using a subtraction, as shown in attachments g4-ss2 and g4-ss4.
> > 
> > This configuration results in weird energy deposits inside the
> > calorimeter. Could this be due to an overlap between c1 and c2? When I
> > remove c2 completely, I still get the same unexpected results, which
> > makes me think the geometry is implemented fine. This has been causing
> > me some grief for a while and so wanted an expert's opinion/advice.
> > 
> > Thanks in advance,
> > 
> > Vince.
> > 
> >    Attachment:
> >       http://hypernews.slac.stanford.edu/HyperNews/geant4/get/AUX/2015/05/14/10.42-19079-g4-ss1.png
> >       http://hypernews.slac.stanford.edu/HyperNews/geant4/get/AUX/2015/05/14/10.42-38003-g4-ss3.png
> >       http://hypernews.slac.stanford.edu/HyperNews/geant4/get/AUX/2015/05/14/10.42-42450-g4-ss2.png
> >       http://hypernews.slac.stanford.edu/HyperNews/geant4/get/AUX/2015/05/14/10.42-59318-g4-ss4.png
> > 
> 
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